The manufacturing of osteosynthesis materials from absorbable polymers is known from several patents. The manufacturing of absorbable sutures and surgical elements from polyglycolide (PGA) ##STR1## has been described in U.S. Pat. No. 3,297,033 and U.S. Pat. No. 3,739,773.
Sutures manufactured from polylactide (PLA) ##STR2## are described in U.S. Pat. No. 2,703,316.
Sutures manufactured from glycolide/lactide copolymers (PGA/PLA) ##STR3## (where n and m are integers &gt;1) are described in U.S. Pat. No. 3,839,297.
Sutures and osteosynthesis devices which are manufactured from poly-.beta.-hydroxybutyric acid (PHB) ##STR4## are described in G.B. Pat. No. 1 034 123.
Sutures and osteosynthesis devices which are manufactured from polydioxanone (PDS) ##STR5## are described in U.S. Pat. No. 4,052,988.
Absorbable surgical devices which are manufactured from polyesteramides (PEA) ##STR6## are described in U.S. Pat. No. 4,343,931.
Absorbable surgical sutures and surgical devices, which are constructed of copolymer which contains units with the structural formula (VII) ##STR7## as end sequences and the units with the formula (VII) combined randomly with the units (VIII) ##STR8## as middle sequence, are described in FI Pat. Appl. No. 83 2405.
Absorbable surgical devices of the above patents and patent applications are typically plates which are fixed to bones by screws, cylindrical medullary nails or corresponding structures which are manufactured by melting an absorbable polymer and by molding or pressing the melt into the suitable form. The mechanical strengths of such samples, which are manufactured by melt processing techniques, have typically the same order of magnitude as those of other similar synthetic polymers. Accordingly the tensile strengths of dry, unhydrolyzed samples manufactured about PBA, PLA, PHB and PGA/PLA have typically the order of magnitude of 40-80 MPa (see e.g. Kulkarni, R. K., Moore, E. G., Hegyeli, A. F. and Fred, L., J. Biomed. Mater. Res., 1971, 5, 169, Vert, M., Chabot, F. and Leray, J., Makromol. Chem., Suppl. 1981, 5, 30, Christel, P., Chabot, F., Leray, J. L., Morin, C. and Vert, M., in Biomaterials (Eds. G. D. Winter, D. F. Gibbons and H. Plenk, Jr.), Wiley (1980), p. 271, Tunc, D. C., Transactions of 9th Annual Meeting of the Society for Biomaterials, Birmingham, USA, 1983, p. 47, Howells, E. R., Chem. Ind., 1982, 7, 509).
The tensile strengths given above are modest when compared to the strengths of compact bone (ca. 80-200 MPa). Additionally melt processed homogeneous polymeric samples of the above polymers are in several cases brittle or too flexible to be used for bone surgical applications. Therefore the conventional applications of resorbable polymers in bone surgery have encountered severe difficulties.
The initial mechanical strength of surgical absorbable osteosynthesis materials has been improved.
For example, U.S. Pat. No. 4,279,249 suggests manufacturing composites consisting of a matrix of a lactic acid homopolymer, or a copolymer very high in lactic acid units and of discrete reinforcements (such as fibers, threads, films, tissues, plaits or poles) made of glycolic acid homopolymer or copolymers predominant in glycolic acid units. The mechanical strength of absorbable polymers has been increased also with bio-stable carbon fibers (J. Kilpikari, Lic. Thesis, Tampere Univ. of Technology, Tampere, Finland, 1985). In the case of known absorbable and partially absorbable composites the chemical element composition of the reinforcements differs from that of the matrix material and; therefore, the matrix and reinforcements cannot form, as a rule, strong chemical primary or secondary bonds with each other which leads to poor adhesion between material components.
Adhesion promoters, such as silanes or titanates etc., which are usually applied in polymeric reinforced composites, cannot be applied in surgical materials intended to be used in surgery because of their toxicity. Therefore good adhesion between matrix and reinforcement units of different chemical origin is difficult to achieve.